Device and Method of Handling Channel Access in Unlicensed Band

ABSTRACT

A method of handling channel access in an unlicensed band comprises initiating a first channel access procedure according to a first channel access priority class for at least one first packet which is scheduled to be transmitted in a first duration on a carrier in an unlicensed band; setting a first counter in the first channel access procedure; initiating a second channel access procedure according to a second channel access priority class for at least one second packet which is scheduled to be transmitted on the carrier; setting a second counter in the second channel access procedure; transmitting the at least one second packet in a second duration on a first frequency resource on the carrier; and transmitting the at least one first packet in the first duration on a second frequency resource on the carrier.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division application of U.S. application Ser. No. 15/638,395,filed on Jun. 30, 2017, which claims the benefit of U.S. ProvisionalApplication No. 62/356,555 filed on Jun. 30, 2016 and No. 62/368,195filed on Jul. 29, 2016.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a device and a method used in awireless communication system, and more particularly, to a device and amethod of handling channel access in an unlicensed band.

2. Description of the Prior Art

A long-term evolution (LTE) system continuously increases peak data rateand throughput by using advanced techniques, such as carrier aggregation(CA), dual connectivity, licensed-assisted access (LAA), etc.

In the LAA, a base station (BS) transmits an uplink (UL) grant for atransmission in a transmission time interval (TTI) on an unlicensedcarrier, to the UE. The UE performs a listen-before-talk (LBT) procedure(or called channel access procedure) before performing the ULtransmission in the TTI on the unlicensed carrier. However, the UL grantis not valid anymore once the UE misses performing the UL transmissionin the TTI. It is not clear how to handle the LBT procedure aftermissing performing the UL transmission in the TTI.

SUMMARY OF THE INVENTION

The present invention therefore provides a communication device forhandling channel access in an unlicensed band to solve theabovementioned problem.

A communication device for handling channel access in an unlicensed bandcomprises a storage device for storing instructions and a processingcircuit coupled to the storage device. The processing circuit isconfigured to execute the instructions stored in the storage device. Theinstructions comprise initiating a first channel access procedureaccording to a first channel access priority class for at least onefirst packet which is scheduled to be transmitted in a first duration ona carrier in an unlicensed band; setting a first counter in the firstchannel access procedure; initiating a second channel access procedureaccording to a second channel access priority class for at least onesecond packet which is scheduled to be transmitted on the carrier, whilerunning the first channel access procedure; setting a second counter inthe second channel access procedure; transmitting the at least onesecond packet in a second duration on a first frequency resource on thecarrier, when the first counter is not decreased to a firstpredetermined value and the second counter is decreased to a secondpredetermined value; and transmitting the at least one first packet inthe first duration on a second frequency resource on the carrier, whenthe first counter is decreased to the first predetermined value and thesecond counter is not decreased to the second predetermined value.

A communication device for handling channel access in an unlicensed bandcomprises a storage device for storing instructions and a processingcircuit coupled to the storage device. The processing circuit isconfigured to execute the instructions stored in the storage device. Theinstructions comprise initiating a channel access procedure on a carrierin an unlicensed band according to a first channel access priority classfor at least one first packet; setting a counter to a first valueaccording to the first channel access priority class in the channelaccess procedure; generating or receiving at least one second packetwhile running the channel access procedure, wherein the at least onesecond packet is associated to a second channel access priority class;updating the channel access procedure by updating the counter to asecond value according to the second channel access priority class; andtransmitting the at least one second packet in a duration on a firstfrequency resource on the carrier, when the counter is decreased to apredetermined value.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a table of channel access priority classes according to anexample of the present invention.

FIG. 5 is a flowchart of a process according to an example of thepresent invention.

FIG. 6 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a wireless communication system 10according to an example of the present invention. The wirelesscommunication system 10 is briefly composed of a network and a pluralityof communication devices. The network and a communication device maycommunicate with each other via one or more carriers of licensed band(s)and/or unlicensed band(s).

In FIG. 1, the network and the communication devices are simply utilizedfor illustrating the structure of the wireless communication system 10.The network may be a radio access network (RAN) including at least oneevolved Node-B (eNB) and/or gNB (or called 5G BS or new radio (NR) BS).In general, a BS may also be used to refer any of the eNB and the gNB.

A communication device may be a user equipment (UE), a machine typecommunication (MTC) device, a mobile phone, a laptop, a tablet computer,an electronic book, a portable computer system, a vehicle, or anaircraft. In addition, the network and the communication device can beseen as a transmitter or a receiver according to direction (i.e.,transmission direction), e.g., for an uplink (UL), the communicationdevice is the transmitter and the network is the receiver, and for adownlink (DL), the network is the transmitter and the communicationdevice is the receiver.

FIG. 2 is a schematic diagram of a communication device 20 according toan example of the present invention. The communication device 20 may bea communication device or the network shown in FIG. 1, but is notlimited herein. The communication device 20 may include a processingcircuit 200 such as a microprocessor or Application Specific IntegratedCircuit (ASIC), a storage device 210 and a communication interfacingdevice 220. The storage device 210 may be any data storage device thatmay store a program code 214, accessed and executed by the processingcircuit 200. Examples of the storage device 210 include but are notlimited to a subscriber identity module (SIM), read-only memory (ROM),flash memory, random-access memory (RAM), hard disk, optical datastorage device, non-volatile storage device, non-transitorycomputer-readable medium (e.g., tangible media), etc. The communicationinterfacing device 220 includes at least one transceiver and is used totransmit and receive signals (e.g., data, messages and/or packets)according to processing results of the processing circuit 200.

In the following embodiments, a UE is used to represent a communicationdevice in FIG. 1, to simplify the illustration of the embodiments.

FIG. 3 is a flowchart of a process 30 according to an example of thepresent invention. The process 30 can be utilized in a UE, for handlinga LBT procedure in an unlicensed band. The process 30 includes thefollowing steps:

Step 300: Start.

Step 302: Receive a UL grant from a network, wherein the UL grantindicates the UE to perform an UL transmission in a transmission timeinterval (TTI).

Step 304: Perform the LBT procedure on a first carrier in response tothe UL grant.

Step 306: Abort the LBT procedure, when the UE senses the first carrierto be busy before the TTI according to the LBT procedure.

Step 308: End.

According to process 30, when the UE fails to perform an UL transmissionin a TTI according to an UL grant due to carrier busy detected by theLBT procedure on a carrier, the UE aborts the LBT procedure. Thus, theUE does not waste power to sense (i.e., receive) the carrier.

Realization of the process 30 is not limited to the above description.The following examples may be applied to the process 30.

In one example, the UE performs the UL transmission on a first carrieraccording to the UL grant, after the UE senses the first carrier to beidle before the TTI according to the LBT procedure.

In one example, the UL grant is transmitted by a BS in the network tothe UE on the first carrier or on a second carrier. The second carriermay be a licensed carrier or an unlicensed carrier. The UL grant may betransmitted by the BS on a physical DL control channel (PDCCH), anenhanced PDCCH (EPDCCH), a machine-type-communications (MTC) PDCCH(MPDCCH), a narrowband PDCCH (NPDCCH) or a shortened PDCCH (sPDCCH)scrambled with a cell radio network temporary identifier (C-RNTI). TheUL grant may include a resource block assignment, a modulation andcoding scheme (MCS), a new data indicator or a hybrid automatic repeatrequest (HARQ) process number.

The LBT procedure may be performed according to the following examples.

The UE may perform a transmission on a carrier in a TTI according to anUL grant received from a BS, after sensing the channel to be idle duringslot durations of a defer duration T_(d), and after the counter N_(p) is0 in Step (4) of the steps below. The counter N_(p) is adjusted bysensing the channel for additional slot duration(s) according to thefollowing steps:

(1) set N_(p)=N_(init,p), where N_(init,p) is a random number uniformlydistributed between 0 and CW_(p), and go to Step (4);

(2) if N_(p)>0 and the UE chooses to decrement the counter, setN_(p)=N_(p)−1;

(3) sense the channel for an additional slot duration, and if theadditional slot duration is idle, go to Step (4); else, go to Step (5);

(4) if N_(p)=0, stop; else, go to Step (2).

(5) sense the channel until either a bust slot is detected within anadditional defer duration T_(d) or all slots of the additional deferduration T_(d) are detected to be idle;

(6) if the channel is sensed to be idle during all the slot durations ofthe additional defer duration T_(d), go to Step (2); else, go to Step(5).

The defer duration T_(d) may include a duration of 16 us≤T_(f)≤16us+T_(s) immediately followed by m_(p) consecutive slot durations whereeach slot duration is 9 us≤T_(sl)≤9 us+T_(s). T_(f) may include an idleslot duration T_(sl) at a start of T_(f). The slot duration T_(sl) isconsidered to be idle, if the BS senses the channel during the slotduration and power detected by the BS for at least 4 μs within the slotduration is less than an energy detection threshold X_(Thresh).Otherwise, the slot duration T_(sl) is considered to be busy.

In one example of Step (1), the BS draws a random number, and transmitsthe random number to the UE in the UL grant. Alternatively, the UE drawsthe random number and adjusts the contention window as follows.CW_(min,p)≤CW_(p)≤CW_(max,p) is the contention window. CW_(p) adjustmentmay be performed according to the following examples. CW_(min,p) andCW_(max,p) are chosen during Step (1) of the above procedure. In oneexample, m_(p), CW_(min,p) and CW_(max,p) are based on a channel accesspriority class p associated with the transmission, as shown in a table40 in FIG. 4. The table 40 includes channel access priority classes withcorresponding parameters according to an example of the presentinvention. The UE may not continuously perform transmission(s) on achannel for a period exceeding T_(mcot,p) as stated in the Table 40. Forthe channel access priority class p=3 and p=4, if the absence of anyother technology sharing the carrier can be guaranteed on a long termbasis (e.g., by level of regulation), T_(mcot,p)=10 ms, otherwise,T_(mcot,p)=8 ms.

In one example, when the UE aborts the LBT procedure, the UE does notcounter down the counter N. In addition, the UE may not sense the firstcarrier until receiving a next UL grant.

In one example, the UL grant indicates a plurality of transmissions(including the first transmission) in a plurality of TTIs (including thefirst TTI). The UE may perform the LBT procedure independently for eachof the plurality of transmissions in a TTI in the plurality of TTIs.

In one example, if the UL grant indicates a plurality of transmissionsin a plurality of TTIs, the UL transmission may be the last transmissionof the plurality of transmissions and the UL transmission is in the lastTTI of the plurality of TTIs. The UE may initiate the LBT procedure forthe earliest UL transmission of the plurality of transmissions in theearliest TTI of the plurality of TTIs. The UE has not sensed the firstcarrier to be idle before the last TTI of the plurality of TTIs in theLBT procedure.

In one example, the TTI includes a subframe, a time slot, two orthogonalfrequency-division multiplexing (OFDM) symbols or four OFDM symbols.

It should be noted that the “random” described above may be interpretedas “pseudo random”. The contents related to each channel access priorityclass in Table 40 may be changed, or a new channel access priority class(e.g., for radio resource control (RRC) and/or non-access stratum (NAS)message) may be added to the Table 40.

FIG. 5 is a flowchart of a process 50 according to an example of thepresent invention. The process 50 can be utilized in a communicationdevice (a UE or a BS), for handling a transmission in an unlicensedband. The process 50 includes the following steps:

Step 500: Start.

Step 502: Initiate a first channel access procedure according to a firstchannel access priority class for at least one first packet which isscheduled to be transmitted in a first duration on a carrier in anunlicensed band.

Step 504: Set a first counter in the first channel access procedure.

Step 506: Initiate a second channel access procedure according to asecond channel access priority class for at least one second packetwhich is scheduled to be transmitted on the carrier, while running thefirst channel access procedure.

Step 508: Set a second counter in the second channel access procedure.

Step 510: Transmit the at least one second packet in a second durationon a first frequency resource on the carrier, when the first counter isnot decreased to a first predetermined value and the second counter isdecreased to a second predetermined value.

Step 512: Transmit the at least one first packet in the first durationon a second frequency resource on the carrier, when the first counter isdecreased to the first predetermined value and the second counter is notdecreased to the second predetermined value.

Step 514: End.

According to process 50, the communication device performs the twochannel access procedures in parallel. The communication devicedetermines transmitting the at least one first packet according to aresult of the first channel access procedure and determines transmittingthe at least second packet according to a result of the second channelaccess procedure.

Realization of the process 50 is not limited to the above description.The following examples may be applied to the process 50.

In one example, the first and second channel access priority classes aredifferent. The communication device may initiate the second channelaccess procedure, when the second channel access priority class isdifferent from the first channel access priority class. In one example,the first channel access priority class and the second channel accesspriority class are the same. The communication device may not initiatethe second channel access procedure, when the first and second channelaccess priority classes are the same.

In one example, the first duration and the second duration are the sameor different. The first duration and the second duration may be one TTIor multiple TTIs. In one example, the first and second predeterminedvalues are the same (e.g., 0), i.e., no difference between differentchannel access priority classes. In one example, the first and secondpredetermined values are different for different channel access priorityclasses.

In one example, when the communication device is a BS, the at least onefirst packet is received from a network (e.g., a mobility managemententity (MME), a gateway or another BS). In one example, when thecommunication device is a BS, the at least one second packet is receivedfrom the network while the BS is running the first channel accessprocedure.

In one example of Step 510, the communication device transmits the atleast one first packet in the second duration on a third frequencyresource (i.e., the remaining frequency resource) on the carrier, if thecommunication device does not use all frequency resources on the carrierin the second duration to transmit all of the at least one second packetor if a transport block size assigned by the BS in an UL grant canaccommodate more than all of the at least one second packet. If thecommunication device does not transmit all of the at least one firstpacket in the second duration on the third frequency resource (i.e., theremaining frequency resource) on the carrier, the communication devicedoes not stop the first channel access procedure. If the communicationdevice needs to transmit at least one third packet (e.g., an IP packetor a NAS message) associated to the first channel access priority whilerunning the first channel access procedure, the communication devicedoes not initiate a third channel access procedure for the at least onethird packet. If the communication device transmits all of the at leastone first packet, the communication device stops the first channelaccess procedure. Then, when the communication device receives orgenerates the at least one third packet, the communication deviceinitiates the third channel access procedure according to the firstchannel access priority class. The communication device may transmit theat least one first packet and the at least one second packet, afterfirst sensing the channel to be idle during the slot durations of asecond defer duration T_(d). The communication device may determine thesecond duration and the second defer duration according to the secondchannel access priority class. The communication device may receive theat least one third packet from the network or generate the at least onethird packet by itself.

In one example of Step 512, the communication device transmits the atleast one second packet in the first duration on a fourth frequencyresource (i.e., the remaining frequency resource) on the carrier, if thecommunication device does not use all frequency resources on the carrierin the first duration to transmit all of the at least one first packetor if a transport block size assigned by the BS in an UL grant canaccommodate more than all of the at least one first packet. If thecommunication device does not transmit all of the at least one secondpacket in the first duration on the fourth frequency resource (i.e., theremaining frequency resource) on the carrier, the communication devicedoes not stop the second channel access procedure. If the communicationdevice needs to transmit at least one fourth packet associated to thesecond channel access priority while running the second channel accessprocedure, the communication device does not initiate a fourth channelaccess procedure for the at least one fourth packet. If thecommunication device transmits all of the at least one second packet,the communication device stops the second channel access procedure.Then, when the communication device receives or generates the at leastone fourth packet, the communication device initiates the fourth channelaccess procedure according to the second channel access priority class.The communication device may transmit the at least one first packet andthe at least one second packet after first sensing the channel to beidle during the slot durations of a first defer duration T_(d). Thecommunication device may determine the first duration and the firstdefer duration according to the first channel access priority class. Thecommunication device may receive the at least one fourth packet from thenetwork or generate the fourth packet by itself.

In one example, when the communication device is the BS, the at leastone first packet belongs to at least one first UE. The at least onesecond packet may belong to at least one second UE. The at least onefirst UE and the at least one second UE may have a same UE or no sameUEs. The third packet may belong to one of the at least one first UE orthe at least one second UE.

FIG. 6 is a flowchart of a process 60 according to an example of thepresent invention. The process 60 can be utilized in a communicationdevice (a UE or a BS), for handling a transmission in an unlicensedband. The process 60 includes the following steps:

Step 600: Start.

Step 602: Initiate a channel access procedure on a carrier in anunlicensed band according to a first channel access priority class forat least one first packet.

Step 604: Set a counter to a first value according to the first channelaccess priority class in the channel access procedure.

Step 606: Generate or receive at least one second packet while runningthe channel access procedure, wherein the at least one second packet isassociated to a second channel access priority class.

Step 608: Update the channel access procedure by updating the counter toa second value according to the second channel access priority class.

Step 610: Transmit the at least one second packet in a duration on afirst frequency resource on the carrier, when the counter is decreasedto a predetermined value.

Step 612: End.

According to process 60, the communication device performs a channelaccess procedure for different packets which are associated to differentchannel access priority classes and are scheduled to be transmitted onthe carrier.

Realization of the process 60 is not limited to the above description.The following examples may be applied to the process 60.

In one example, the communication device updates the channel accessprocedure according to the second channel access priority class when thesecond channel access priority class is different from the first channelaccess priority class. That is, the communication device updates thecounter to a second value. In one example, the communication deviceupdates the channel access procedure, when the second value is smallerthan a current value of the counter. When the counter is decreased tothe predetermined value (e.g., 0) in the channel access procedure, thecommunication device transmits the at least one second packet in theduration on the carrier.

In one example, the at least one first packet is associated to the firstchannel access priority class.

In one example, when the communication device is a BS, the at least onefirst packet is received from a network. In one example, when thecommunication device is a BS, the at least one second packet is receivedfrom the network. The at least one second packet is associated to thesecond channel access priority class.

In one example, the communication device generates the at least onefirst packet and the at least one second packet.

In one example of Step 610, the communication device transmits at leastone of the at least one first packet in the duration on a secondfrequency resource (i.e., the remaining frequency resource) on thecarrier, if the communication device does not use all frequencyresources on the carrier in the duration to transmit all of the at leastone second packet or if a transport block size assigned by the BS in anUL grant can accommodate more than all of the at least one secondpacket. The communication device may transmit the at least one firstpacket and the at least one second packet after first sensing thechannel to be idle during the slot duration s of a defer duration T_(d).The communication device may determine the duration and the deferduration according to the second channel access priority class. If thecommunication device generates or receives at least one third packetassociated to the second channel access while running the channel accessprocedure after updating the channel access procedure, the communicationdevice may not update the channel access procedure again. If thecommunication device generates or receives the at least one third packetassociated to the first channel access priority class or a third channelaccess priority class while running the channel access procedure afterupdating the channel access procedure, the communication device mayupdate the channel access procedure again according to the first channelaccess priority class or the third channel access priority class. Thecommunication device may update the channel access procedure by updatingthe counter to a third value. In one example, the communication devicemay update the channel access procedure, when the third value is smallerthan a current value of the counter. When the counter is decreased tothe predetermined value (e.g., 0), the communication device transmitsthe at least one third packet after first sensing the channel to be idleduring the slot durations of a defer duration T_(d). The communicationdevice may determine the duration and the defer duration according tothe third channel access priority class. If the communication devicedoes not use all frequency resources on the carrier in the duration totransmit the at least one third packet, the communication device mayfurther transmit the at least one first packet or the at least onesecond packet in the duration on the remaining frequency resources onthe carrier in the duration.

In one example, the communication device may receive the at least onethird packet from the network when the communication device is the BS.

The following examples may be applied to the processes above.

In one example, the at least one first packet is associated to the firstchannel access priority class, and includes at least one of an IPpacket, a RRC message, a NAS message, a PDCP PDU, a RLC PDU and a MACPDU. In one example, the at least one second packet is associated to thesecond channel access priority class, and includes at least one of an IPpacket, a RRC message, a NAS message, a PDCP PDU, a RLC PDU and a MACPDU.

In one example, each of the at least one third and fourth packetsincludes at least one of an IP packet, a RRC message, a NAS message, aPDCP PDU, a RLC PDU and a MAC PDU.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned description and examples. Theabovementioned description, steps and/or processes including suggestedsteps can be realized by means that could be hardware, software,firmware, an electronic system, or combination thereof. An example ofthe means may be the communication device 20. Any of the above processesand examples above may be compiled into the program code 214.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A communication device for handling channelaccess in an unlicensed band, comprising: a storage device, for storinginstructions of: initiating a first channel access procedure accordingto a first channel access priority class for at least one first packetwhich is scheduled to be transmitted in a first duration on a carrier inan unlicensed band; setting a first counter in the first channel accessprocedure; initiating a second channel access procedure according to asecond channel access priority class for at least one second packetwhich is scheduled to be transmitted on the carrier, while running thefirst channel access procedure; setting a second counter in the secondchannel access procedure; transmitting the at least one second packet ina second duration on a first frequency resource on the carrier, when thefirst counter is not decreased to a first predetermined value and thesecond counter is decreased to a second predetermined value; andtransmitting the at least one first packet in the first duration on asecond frequency resource on the carrier, when the first counter isdecreased to the first predetermined value and the second counter is notdecreased to the second predetermined value; and a processing circuit,coupled to the storage device, configured to execute the instructionsstored in the storage device.
 2. The communication device of claim 1,wherein the first channel access priority class and the second channelaccess priority class are different.
 3. The communication device ofclaim 1, wherein the at least one first packet is associated to thefirst channel access priority class, and comprises at least one of aninternet protocol (IP) packet, a radio resource control (RRC) message, anon-access stratum (NAS) message, a packet data convergence protocol(PDCP) protocol data unit (PDU), a radio link control (RLC) PDU and amedium access control (MAC) PDU; and the at least one second packet isassociated to the second channel access priority class, and comprises atleast one of an IP packet, a RRC message, a NAS message, a PDCP PDU, aRLC PDU and a MAC PDU.
 4. The communication device of claim 1, whereinthe at least one first packet is received from a network, and the atleast one second packet is received from the network while thecommunication device is running the first channel access procedure. 5.The communication device of claim 1, wherein the storage device furtherstores the instruction of: transmitting the at least one first packet inthe second duration on a third frequency resource on the carrier.
 6. Thecommunication device of claim 1, wherein the storage device furtherstores the instruction of: transmitting the at least one second packetin the first duration on a fourth frequency resource on the carrier. 7.A communication device for handling channel access in an unlicensedband, comprising: a storage device, for storing instructions of:initiating a channel access procedure on a carrier in an unlicensed bandaccording to a first channel access priority class for at least onefirst packet; setting a counter to a first value according to the firstchannel access priority class in the channel access procedure;generating or receiving at least one second packet while running thechannel access procedure, wherein the at least one second packet isassociated to a second channel access priority class; updating thechannel access procedure by updating the counter to a second valueaccording to the second channel access priority class; and transmittingthe at least one second packet in a duration on a first frequencyresource on the carrier, when the counter is decreased to apredetermined value; and a processing circuit, coupled to the storagedevice, configured to execute the instructions stored in the storagedevice.
 8. The communication device of claim 7, wherein the at least onefirst packet is associated to the first channel access priority class,and comprises at least one of an internet protocol (IP) packet, a radioresource control (RRC) message, a non-access stratum (NAS) message, apacket data convergence protocol (PDCP) protocol data unit (PDU), aradio link control (RLC) PDU and a medium access control (MAC) PDU. 9.The communication device of claim 7, wherein the at least one secondpacket is associated to the second channel access priority class, andcomprises at least one of an IP packet, a RRC message, a NAS message, aPDCP PDU, a RLC PDU and a MAC PDU.
 10. The communication device of claim7, wherein the storage device further stores the instruction of:transmitting at least one of the at least one first packet in theduration on a second frequency resource on the carrier.
 11. A method ofhandling channel access in an unlicensed band for a communicationdevice, the method comprising: initiating a first channel accessprocedure according to a first channel access priority class for atleast one first packet which is scheduled to be transmitted in a firstduration on a carrier in an unlicensed band; setting a first counter inthe first channel access procedure; initiating a second channel accessprocedure according to a second channel access priority class for atleast one second packet which is scheduled to be transmitted on thecarrier, while running the first channel access procedure; setting asecond counter in the second channel access procedure; transmitting theat least one second packet in a second duration on a first frequencyresource on the carrier, when the first counter is not decreased to afirst predetermined value and the second counter is decreased to asecond predetermined value; and transmitting the at least one firstpacket in the first duration on a second frequency resource on thecarrier, when the first counter is decreased to the first predeterminedvalue and the second counter is not decreased to the secondpredetermined value.
 12. The method of claim 11, wherein the firstchannel access priority class and the second channel access priorityclass are different.
 13. The method of claim 11, wherein the at leastone first packet is associated to the first channel access priorityclass, and comprises at least one of an internet protocol (IP) packet, aradio resource control (RRC) message, a non-access stratum (NAS)message, a packet data convergence protocol (PDCP) protocol data unit(PDU), a radio link control (RLC) PDU and a medium access control (MAC)PDU; and the at least one second packet is associated to the secondchannel access priority class, and comprises at least one of an IPpacket, a RRC message, a NAS message, a PDCP PDU, a RLC PDU and a MACPDU.
 14. The method of claim 11, wherein the at least one first packetis received from a network, and the at least one second packet isreceived from the network while the communication device is running thefirst channel access procedure.
 15. The method of claim 11, wherein themethod further comprises: transmitting the at least one first packet inthe second duration on a third frequency resource on the carrier. 16.The method of claim 11, wherein the method further comprises:transmitting the at least one second packet in the first duration on afourth frequency resource on the carrier.